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in britain, for example, people thought it would make them sick because it looked like a harmful plant. in addition, it sometimes caused lead poisoning among the rich, as they ate the acidic tomatoes on expensive plates made of materials containing lead. poor people, however, did not have this problem since they used cheap plates made of wood. therefore, tomatoes were only eaten by poor people until the 19th century.
this changed after many italians moved to america during the 19th and 20th centuries. they brought with them dishesmade with tomatoes, such as pizza and spaghetti, which many people enjoyed. this helpedspread the tomato’s popularity to other cultureswhich the italians came into contact with in america, and eventually to the world.
고1능률(이찬승) 교과서에 special lesson에 있는 지문 내용의 중의 일부입니다.

1. them 이 가리키는 것이 무엇인지 잘 모르겠어요.... them이 뭘 가리키는 거죠??

2. 밑줄 친 this helpedspread ~ 문장 해석 좀 부탁드리겠습니다.. 해석이 매끄럽게 되지 않아서요..ㅜㅠ

친절한 답변 꼭 부탁 드립니다.